American Association of Clinical Endocrinologists and American College of Endocrinology Disease State Clinical Review: The Increasing Incidence of Thyroid Cancer

Abstract

Objective (1) Describe current epidemiology of thyroid cancer in the United States; (2) evaluate hypothesized causes of the increased incidence of thyroid cancer; and (3) suggest next steps in research and clinical action. Methods Analysis of data from Surveillance, Epidemiology and End Results System and the National Center for Vital Statistics. Literature review of published English-language articles through December 31, 2013. Results The incidence of thyroid cancer has tripled over the past 30 years, whereas mortality is stable. The increase is mainly comprised of smaller tumors. These facts together suggest the major reason for the increased incidence is detection of subclinical, nonlethal disease. This has likely occurred through: health care system access, incidental detection on imaging, more frequent biopsy, greater volumes of and extent of surgery, and changes in pathology practices. Because larger-size tumors have increased in incidence also, it is possible that there is a concomitant true rise in thyroid cancer incidence. The only clearly identifiable contributor is radiation exposure, which has likely resulted in a few additional cases annually. The contribution of the following causes to the increasing incidence is unclear: iodine excess or insufficiency, diabetes and obesity, and molecular disruptions. The following mechanisms do not currently have strong evidence to support a link with the development of thyroid cancer: estrogen, dietary nitrate, and autoimmune thyroid disease. Conclusion Research should focus on illuminating which thyroid cancers need treatment. Patients should be advised of the benefits as well as harms that can occur with treatment of incidentally identified, small, asymptomatic thyroid cancers.

Prevalence of Contralateral Tumors in Patients with Follicular Variant of Papillary Thyroid Cancer

“…Patients with fvPTC have historically been treated similarly to those with cPTC, including thyroidectomy and radioactive iodine ablation, due in part to studies demonstrating equivalent prognosis. 4,[20][21][22] However, with the increased awareness about clinicopathologic differences in fvPTC subtypes, some authors have suggested that thyroid lobectomy alone might be appropriate for certain encapsulated tumors, such as NIFTP. [17][18][19] In this study, we sought to define the prevalence of synchronous multifocal and bilateral disease in fvPTC to improve decision making about the extent of surgical resection.…”

“…[1][2][3][4] The majority of these malignancies are well-differentiated thyroid cancers, including papillary thyroid carcinoma (PTC) and follicular thyroid carcinoma. After the classical type (cPTC), the follicular variant of papillary thyroid carcinoma (fvPTC) is the most common subtype, accounting for up to 41% of all PTC cases.…”

Thyroid cancer incidence in Canada: a national cancer registry analysis

“…6 Most of the recent increase in incidence is due to papillary thyroid cancer, 1,3,4 which generally has an indolent course; only a small proportion of these cancers behave aggressively and very few patients die. 7 There is thus the potential for overdiagnosis and overtreatment of lesions that if left alone would never cause any problems. 8 Choosing Wisely Canada has indicated that the early detection of small thyroid lesions contributes to overdiagnosis and suggests limiting use of thyroid ultrasound.…”

What is the right dose of modern medicine?

“…Most of the increase in incidence has occurred in small papillary carcinomas 13 where the outlook in terms of prognosis is excellent 18 . There appears to be no adequate explanation for the upward trend in incidence in terms of changes in known risk factors such as childhood exposure to ionizing radiation, trends in diabetes, obesity or reproductive patterns or the availability of nutritional iodine 19 . The most likely explanation is a change in the way the condition is diagnosed in the context of what is now understood to be a large reservoir of cases of subclinical disease 13 .…”